Contacts for pantograph switch



1967 E. R. PERRY ETAL. 3,35%,520

CONTACTS FOR PANTOGRAPH SWITCH 2 Sheets-Sheet 1 Filed April 6, 1967 Oct. 31, 1967 PERRY ETAL I 3,350,520

CONTACTS FOR PANTOGRAPH SWITCH Filed April 6, 1967 2 SheetsSheet 2 Md/Mp 1 IA 592ml,

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United States Patent 3,350,520 CONTACTS FOR PANTOGRAPH SWITCH Elijah R. Perry, Jerry L. Mundon, and Albert M. Frey,

Portland, 0reg., assignors to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Apr. 6, 1967, Ser. No. 628,946 8 Claims. (Cl. 20048) ABSTRACT OF THE DISCLOSURE A stationary contact assembly comprising four parallel spaced apart relatively flexible conductive bars is suspended from an electrical transmission line. One end of each bar is connected to the line and the other end is insulated therefrom. A pair of two conductor jaws of a pantograph switch close on the bars so that each jaw engages two bars. Current flows along the two conductors of each jaw and along each of the two bars to create a magnetic field causing improved contact engagement. Flexibility of the bars also allows ice breaking.

This invention relates generally to electrical switch contacts and particularly to stationary contact assemblies for cooperation with the movable jaws of pantograph type disconnect switches.

One type of pantograph switch employed with 350 to 500 kv. electrical power transmission lines comprises a pair of pivotable jaws which, when closing, move toward and clamp a stationary contact assembly and which, when opening, release and move away from the stationary contact assembly. Heretofore, the stationary contact assembly comprised a single electrically conductive bar supported between a pair of electrically conductive brackets. Such stationary contacts and cooperating jaws posed certain problems. For example, high momentary or continuous currents created magnetic fields which tended to open the pantograph switch jaws and impair good electrical contact. Furthermore, if ice formed on the stationary contact bar, it was not easy to break because pantograph switch jaws closing on it merely put it under compression.

Accordingly, it is an object of the present invention to provide improved pantograph switches and stationary contact assemblies therefor.

Another object is to provide such switches and contact assemblies which have improved current carrying capacity and abrasion resistance.

Another object is to provide stationary contact assemblies comprising a plurality of electrically conductive bars which when engaged by the pantograph switch jaws shed any ice formed thereon.

Another object is to provide stationary contact assemblies comprising a plurality of rotatably mounted bars which align perfectly with the pantograph switch jaws.

Another object is to provide pantograph switches and stationary contact assemblies therefor which conduct current so as to create a magnetic field which enhances contact between the stationary contact bars and the pantograph switch jaws.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate a preferred embodiment of the invention but it is to be understood that the embodiment illustrated is susceptible of modifications with respect to details thereof without departing from the scope of the appended claims.

In the drawings:

FIG. 1 is an end elevational view of a pantograph switch and stationary contact assembly in accordance with the present invention;

FIG. 2 is an enlarged side elevational view of a portion of the stationary contact assembly shown in FIG. 1;

FIG. 3 is a view taken along line IIIIII of FIG. 2;

FIG. 4 is an enlarged cross-sectional View taken along line IVIV of FIG. 3; and

FIG. 5 is an isometric view of certain components shown in FIGS. 2, 3, and 4.

Referring to FIG. 1, a pantograph switch 10 is shown in engagement with a stationary contact assembly 12 which is mounted on a transmission line or flexible bus 14. Pantograph switch 10 comprises an insulating support 16, a housing 18 for a hydraulic or manual actuating mechanism (not shown), and a pair of electrically conductive blades 29 and 22. Blade 20 is understood to comprise a lower arm 24 which is pivotally mounted at point 26 to housing 18 and further comprises an upper arm 28 which is pivotally connected at point 30 to the lower arm 24. Upper arm 28 is a U-shaped member which provides two parallel paths for current flow. Blade 22 is similar to blade 20 and comprises an upper arm 31. The upper arms of blades 20 and 22 are pivotally connected to each other at point 29. In FIG. 1, switch 10 is shown in fully closed position and its fully open position is indicated by dotted lines (counter-balance to ease operation).

As FIGS. 1 through 5 show, stationary contact assembly 12 comprises four parallel horizontally mounted conductive bars 32, 34, 36 and 38 which are mounted between a pair of spaced apart brackets 44) and 42 which are electrically and mechanically connected to transmission line 14. As FIGS. 2 and 3 show, bracket 40, which is similar to bracket 42, comprises a portion 44 which adapts it for removable connection to line 14. Bracket 44 further comprises an electrically conductive downwardly depending portion 46 to which an electrically conductive support 48 is attached for connection to the conductive bars. Support 48 comprises an electrically conductive spindle 50 on which an electrically conductive head 52 rotates. Spindle 50 is electrically and mechanically connected to support 48. Preferably, support 48 comprises a corona shield portion 49.

The conductive bars 32, 34, 36 and 38 of stationary contact assembly 12 are flexible rather than rigid which causes any ice forming thereon to be placed in a bending stress rather than compression when the jaws of the pantograph switch close thereon.

In practice, the supports 48 are located approximately thirty-six inches apart from each other. Preferably, the bars are constructed of cadmium copper and hard alloy plated with successive layers of silver and nickel disposed thereon to reduce abrasion caused by vertical movement of the bars due to line sway and temperature changes. The cadmium copper provides a high strength, high conductivity current carrying material, and the successive layers of silver and nickel provide a good current carrying contact with high abrasive resistance.

When pantograph switch 10 is closed, each upper arm 28 and 31 of the pantograph switch blades 20 and 22 come into contact with two of the bars i.e., bars 32 and 34 and bars 36 and 38, respectively. The heads 52 and 53 holding the bars are rotatable with respect to the overhead line which allows the bar of the stationary contact to always perfectly align with the moving contacts 28 and 31 if the pantograph switch jaws.

Under high current short circuit conditions the pantograph switch arms 28 and 31 aiford parallel paths for current flow which results in a magnetic attraction between the two arm members. This attraction results in an increase of contact loading by fifty percent between the arms and their associated bars at the time when it is most useful.

Considering the horizontal bars 32, 33, 36, 33, FIGS. 4 and 5-best show that bars 32 and 36 are insulated from the head 52 on the left-hand end support 48 and are electrically connected to the right-hand end head 53. Bars 34 and 38 are electrically connected to the head 52 on the left-hand end support 48 and are insulated from head 53. This results in an opposing current flow shown by the arrows in FIG. 5 which nullifies any magnetic forces tending to move the contact bars apart. The bars are insulated from their respective beads by insulating means such as the members 55 shown in FIG. 4 in association with bar 36'.

Contact pressure is positively maintained by the mechanical structure of the pantograph switch arms. The pantograph switch is understood to be mechanically locked in closed position by a toggle arrangement in the actuating mechanism going over the center position. The long high strength alloy aluminum blades are deflected approximately seven inches during the closing operation. This deflection maintains the 300 pounds contact force without any critical adjustment.

In practice the pantograph switch jaws close, for example, with a force of 300 pounds. This is 75 pounds per contact point giving a deflection of the top contact flexible bars 32 and 38 of approximately one-fourth inch. This deflection is suflicient to cause cracking of any ice which might form on it. Once the ice is cracked it is very easily dislodged for making full electrical contact.

When stationary contact assembly 12 is mounted on a flexible bus 14, consideration must be given to vertical and side movement. It is recommended, therefore, that flexible bus lengths be limited to a tight span distance of 300 feet between supports. Contact assembly 12 can withstand side winds up to 90 miles per hour and properly compensate for severe temperature variations. Temperature variations can cause a vertical movement of up to twenty-four inches of the stationary contact assembly 12. This movement can result in severe abrasion of contact unless proper precautions are taken as hereinbefore mentioned. The high silver content together with the slight wiping or sliding action between the contacts provides a low resistance current path under the most severe conditions of industrial contamination and other adverse environmental conditions.

The embodiments in which an exclusive property or privilege is claimed are defined as follows:

1. In a stationary contact adapted to be mounted on a power line for cooperation with the movable jaws of a pantograph switch,

a pair of electrically conductive spaced apart brackets electrically and mechanically connected to said line, at least one pair of electrically conductive spaced apart bars supported between said brackets,

each of said bars being adapted to be engaged by one jaw of said switch,

first insulating means for electrically insulating one end of one of said bars from its associated bracket, and

second insulating means for electrically insulating the other end of the other of said bars from its associated bracket.

2. A stationary contact according to claim 1 wherein said pair of bars is rotatably mounted with respect to said brackets.

3. A stationary contact according to claim 1 wherein said bars are flexible.

4. In a stationary contact adapted to be mounted on a power line for cooperation with the movable jaws of a pantograph switch,

a pair of electrically conductive spaced apart brackets electrically and mechanically connected to said line, at least two pairs of electrically conductive spaced apart bars supported between said brackets,

each pair of bars being adapted to be engaged by one jaw of said switch,

first insulating means for electrically insulating one end of one bar in each of said pairs from one of said brackets,

and second insulating means for electrically insulating one end of the other bar in each of said pairs from the other of said brackets. 5. A stationary contact according to claim 4 wherein said two pairs of bars are rotatably mounted with respect to said brackets.

6. A stationary contact according to claim 4 wherein said bars are flexible.

7. In a stationary contact adapted to be mounted on a power line for cooperation with the movable jaws of a pantograph switch,

a pair of electrically conductive spaced apart brackets electrically and mechanically connected to said line,

each bracket comprising a first member detachably connectable to said line and further comprising a second member depending from said first member and rotatably mounted thereon,

at least two pairs of electrically conductive spaced apart bars supported between said brackets,

each pair of bars being adapted to be engaged by one jaw of said switch,

each bar being mechanically supported on said second members, first insulating means for electrically insulating one end of one bar in each of said pairs from one of said second members,

and second insulating means for electrically insulating one end of the other bar in each of said pairs from the other of said second members.

8. A stationary contact according to claim 7 wherein said bars are flexible.

References Cited UNITED STATES PATENTS ROBERT K. SCHAEFER, Primary Examiner.

H, O. JONE Assistant Examiner. 

1. IN A STATIONARY CONTACT ADAPTED TO BE MOUNTED ON A POWER LINE FOR COOPERATION WITH THE MOVABLE JAWS OF A PANTOGRAPH SWITCH, A PAIR OF ELECTRICALLY CONDUCTIVE SPACED APART BRACKETS ELECTRICALLY AND MECHANICALLY CONNECTED TO SAID LINE, AT LEAST ONE PAIR OF ELECTRICALLY CONDUCTIVE SPACED APART BARS SUPPORTED BETWEEN SAID BRACKETS, EACH OF SAID BARS BEING ADAPTED TO BE ENGAGED BY ONE JAW OF SAID SWITCH, FIRST INSULATING MEANS FOR ELECTRICALLY INSULATING ONE END OF ONE OF SAID BARS FROM ITS ASSOCITED BRACKET, AND SECOND INSULATING MEANS FOR ELECTRICALLY INSULATING THE OTHER END OF THE OTHER OF SAID BARS FROM ITS ASSOCIATED BRACKET. 